Mordanting agent



Patented Nov. 3, 1942 3 MORDANTING AGENT Samuel M. Weisberg, Baltimore,- Md.,'and William E. Stringer, Bronx, N. Y., assignorstozseab test, Inc., Maryland Baltimore, Md, a corporation of .No Drawing. Application December 4-, 1939, I

Serial No. 307,450 z 8 Claims.

This invention relates to dyes and relate more particularly to mordants and decomposition or deposition retarding agents for mordants.

Many different types of chemical agents such is, for example, cream of tartar and lactic acid, are used to retard the decomposition and control the rate of deposition of metallic salt mordents in the dyeing of yarn and textiles. Cream of tartar (KHCiHiOs) is perhaps the most commonly used of these retarding agents. However, this composition has the serious disadvantage of being expensive and not readily availabl at all times, inasmuch as it is an imported product.

Lactic acid ha not been entirely satisfactory as a decomposition or deposition retarding agent inasmuch as it does not sufliciently retard or slow down the reduction of such mordants as potassium and sodium bichromates.

Attempts have also been. made to use salts of lactic acid in conjunction with metallic salt mordants but such attempts consistently have been failures, apparently for the reason that th use of these salts was based on erroneous conceptions of their composition. However, it would be highly desirable to use salts of lactic acid as decomposition or deposition retarders for metallic salt mordants inasmuch as the salts of lactic acid are quite inexpensive as compared with cream of tartar, and at the same time ar readily available as a domestic product.

An object of the present invention, accordingly, is to provide metallic mordants containing salts of lactic acid which have a slow and well controlled rate of decomposition or deposition.

Another object of the invention is to provide solutions of salts of lactic acid which act as bufiering agents and decomposition or deposition retarders for metallic salt mordants.

Other objects of the invention will become apparent from the description of typical forms of the invention hereinafter.

It has been discovered that the pH value of solutions of salts of lactic acid bear a direct relationship to their ability to act as retarders in the deposition or decomposition of metallic salt mordants, such as, for example, chromium salts, aluminum salts and tin salts, which are well known and commonly used in the art. From a series of tests it has been determined that solutions of lactate salts should be adjusted to a pH value not less than 4.0 in order to obtain the optimum results. Such lactate salt solutions may be used with those mordants with which cream of tartar has previously been used, for example, sodium or potassium bichromate, chrome alum, stannous chloride, alum and neutral aluminum sulphates. The alkali metal, alkaline earth metal and ammonium salts of lactic acid such as sodium, po-

tassium, calcium, magnesium and ammonium;

lactates are entirely atisfactory. The retarding effects of these salts will vary somewhat with the type of metallic ion with which the lactate ion is associated. That is, for example, sodium lactate is a more rapid reductant than ammonium lactate, and, accordingly, advantage can be taken of these varying characteristics in controlling the rate of deposition of the metallic mordants.

By way of specific example of the effect of' Ldctatef-Bichromate 10H relations Initial PH pH pH :53 After Example after tion of 15 Remarks adding on) min. water mate boiling Water cc Lactic acid (50%) Redictwn rapid, brown gel- 8 2.5 gins" 2. 1 2. 2 6.3 atinous plenum odmm g g tate formed.

#2 Water l00 cc Reduction rapid Sodium lactate (50%) but not as rapid adjusted to pH 4.0 as for (1). Some with lactic acid 3. 5 3. 5 6. 3 brown gelatinous 2.5 gms precipitate but Sodium dichromate not as much as 2.5 gins for (l).

Like #2 but sodium 5. 0 4. 8 6.3 Reduction rate lactate adjusted :moderate. No with lactic acid to precipitate. pH 5.5.

Like #2 but sodium 7.0 5.1 6.3 Do.

lactate adjusted to pH 7.0 with lactic acid.

Like #2 but sodium 8.7 5.0 6. 3 Do.

lactate adjusted to pH 10.0 with sodium hydroxide.

It will be seen from the above table that lactic acid or sodium lactate and sodium bichromate solutions having a pH value of lower than 4.0 are entirely unsatisfactory because of excessively rapid rate of reduction of such mordants and the that sodium lactate has an extremely highflbuf-x fering action inasmuch as in Example #5, the:

sodium lactate solution which was initially adjusted to pH 10.0, upon mixture with sodium bichromate resulted in a solution having a pH value of 5.0, which is very close to the pH value of the solutions disclosed in Examples 3 and 4. It should be understood, of course, that the pH values indicated in column 3 of the above table (pH value after addition of ohromates) are the pH Values of the mordant alone andnot the pH values of the mordant in the presence of a fabric, or other material being dyed. Because of this high buffering action of sodium lactate,

excessive'amounts of alkali are required to pro-.

duce solutions having pH values exceeding 100 and it is not practical to operate above this pH value because of the expense involved. Thereaction of mordants is obtained by the use of such salts, not only by varying their concentration but by utilizing salts of lactic acid which have difierent metallic ions. Accordingly, it will be understood that there may be variations in the proportions of such salts and they may be used in different combinations with various metallic mordants without departing from the invention. The specific examples given above, therefore, should be considered as illustrative only and not as limiting the scope of the following claims.

We claim:

1. A mordant comprising a solution having a pH value between about 4.8 and 5.1 containing a chromium salt and a salt of lactic acid.

2. A mordant comprising a solution having a pH value between about 4.8 and. 5.1 containing sodium bichromate and a salt of lactic acid.

3. A mordant comprising an aqueous solution of a chromate and a salt of lactic acid in about equal proportions, said solution having a pH 7 value between about 4.8 and 5.1.

fore, for practical purposes, lactate solutions having a pH value between-4 and 10 are entirely satisfactory.

The value of lactate solutions has been established by conducting dyeing tests upon wool.

In every instance excellent dyeing results were obtained, using mixtures-of sodium lactate adjusted to a pH value exceeding 4.0 and sodium bichromate.

It will be apparent that solutions of saltsof lactic acid are highly efiective bufiering agents and decomposition retarders and have a wide field of use in the dyeing industry. It will be understood, moreover, that excellent control over the 4. A mordant comprising an aqueous solution of a metallic salt .mordant and a salt of lactic. acid, said solution having a pH value between about 4.8 and 5.1. r

5. A mordant comprising a solution having a pH value between about.4.8 and 5.1 containingof a chromate and sodium lactate in about equal, proportions, .said solution having a .pH value.

between about 4.8 and 5.1.

8. A mordant comprising. an aqueous. solution of a metallic salt mordant and sodium lactate, said solution having a pH valuebetween about 4.8 and 5.1.

SAMUEL M. W'EISBERG.

WILLIAM E. STRINGER. l 

